A couple things that might help you better understand.
1.) Curtis was upset by the placement of Parker's mark. He knows that she likes Parker and had no problem with that as long as he was apart of the equation. He thought that her having his babies would make her have more affection for him. She has repeatedly said that she only wants 1 partner so in Curtis's mind Parker took that place while Curtis only forced his mark on her. (Clearly he was wrong)
2.) Speaking of babies... Curtis dropped the babies on the floor but didn't do anything after that. They walked away saying that "Daddy is mean." Snakes don't usually care for their young anyway. So despite their size those babies are quite independent already. Cubs will need a lot more care so I'm sure we're going to see (unfortunately and unfairly) a lot more of the Parker's cubs than our baby snakes. ಥ‿ಥ
3.) This is a very primal instinct driven world. So territory and dominance are a huuuuge part of claiming spaces and "women" because despite the very female driven society and culture, it is only because there are a few of them. Take notice that men are always stronger and in positions of power. For example: when winston brought those 5 women and he saved 1 of them she was immediately offered to him because it is his right. Although it was her right to refuse which is some power but clearly not enough. Also notice, there are no queens technically, there are only strong kings and their women that they do anything for because they get heirs and sex out of it. (This is one of the reasons I still like Curtis more than Parker.)
So Parker and Curtis treating winston the way that they do is wrong to us and our FL because we come from a more "structured and moral" driven world. While they have laid claim to something. If that something takes winston under her wing then they will partially back down but until then they appreciate help when they need it but refuse to share what is theirs.
Hope this helps to clear some things up.
Writing this notes down
Seriously, where are the babies? They've been unaccounted for for several chapters now. And no one is even saying anything about it. Did the author just forget to mention them or what?
I don't want to believe that Curtis did something to them. Curtis has done some truly heinous shit, but I don't want to believe that he'd hurt his children. And maybe not because they're his. He's never showed much interest in having kids. But because they're Bai's. I want to believe he wouldn't hurt them because they're Bai's.
Also, did he go into a rage because of WHERE Parker's spousal mark showed up? Or because she had one at all? Because he was the one who first said she could 'reproduce' with Parker after she did with him.
Also, those boys need to suck it up and be more welcoming to Winston. They call on him to look after Bai, but then as soon as they don't need him, they're growling at him to get away from her. Rude! Now that things have gotten more serious, they need to keep him around and start treating him like part of the 'family'.
And the Ape king needs to get what's coming to him. I don't want them to kill him. I want him to suffer at length.